Heat waves in graphene could keep circuits cool

March 09, 2015 //
By Jean-Pierre Joosting

A decades long problem electronics is cooling. As electronic components get smaller and faster the more challenging it is to cool it down. One solution to improve the cooling is to use materials with very high thermal conductivity, such as graphene, to quickly dissipate heat and thereby cool down the circuits.

However, currently potential applications are facing a fundamental problem: how does heat propagate inside these sheets of materials that are no more than a few atoms thick?

A recent study published in Nature Communications by a team of EPFL researchers has shed new light on the mechanisms of thermal conductivity in graphene and other two-dimensional materials. The team has demonstrated that heat propagates in the form of a wave, just like sound in air. This was up to now a very obscure phenomenon observed in few cases at temperatures close to the absolute zero. Their simulations provide a valuable tool for researchers studying graphene, whether to cool down circuits at the nanoscale, or to replace silicon in tomorrow's electronics.

If it has been difficult so far to understand the propagation of heat in two-dimensional materials, it is because these sheets behave in unexpected ways compared to their three-dimensional cousins. In fact, they are capable of transferring heat with extremely limited losses, even at room temperature.

Generally, heat propagates in a material through the vibration of atoms. These vibrations are are called "phonons", and as heat propagates though a three-dimensional material, these phonons keep colliding with each other, merging together, or splitting. All these processes can limit the conductivity of heat along the way. Only under extreme conditions, when temperature goes close to the absolute zero (-200 0C or lower), it is possible to observe quasi-lossless heat transfer.